Direct chill casting is a technique in which aluminum or other molten metal is poured into the inlet end of an open-ended mould while liquid coolant is applied to the inner periphery of the mould to solidify the metal as ingot. Also, the same or different coolant is normally applied to the exposed surface of the ingot as it emerges from the outlet end of the mould, to continue the cooling effect on the solidifying metal.
The form of such moulds has been generally standardized because of manufacturing practices and the particular necessities of an internal surface defining in a horizontal plane the periphery of the ingot to be cast. The vertical height of the internal surface of the mould is somewhat limited to alleviate sticking of the cast ingot after solidification of its surface, and to allow immediate impingement of coolant to prevent undesirable physical changes in the ingot. Typical direct chill casting moulds of the above type are described in U.S. Pat. Nos. 3,688,834; 3,739,837 and 4,421,155.
In using such moulds, various problems have been experienced. In particular, the mould configuration tends to skew with use and its individual elements tend to warp, caused primarily by the thermal activities of the casting process. An attempt was made to solve the above problem in the mould described in U.S. Pat. No. 3,688,834 by changing the mould configuration to provide a thicker inner or moulding surface. It was believed that this thicker surface cooperating with the other mould parts would prevent warpage because of its beam effect.
It is an object of the present invention to provide an improved direct chill casting system in which the above problems are avoided.